Automatic system for checking receipt of telegraph messages in numerical order



Oct. 9, 1951 E. F. WATSON 2,570,505 AUTOMATIC SYSTEM FOR CHECKING RECEIET 0F TELEGRAPH MESSAGES IN NUMERICAL ORDER Filed Sept. 9,. 1943 cm: 4 PULL am 0PERATED(1-o ALL aur nag N UPPER us: 21.4 TEN ,4

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Patented Oct. 9, 1951 AUTOMATIC SYSTEM FOR CHECKING RECEIPT OF TELEGRAPH MESSAGES IN NUMERICAL ORDER Edward F. Watson, Larchmont, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application September 9, 1943, Serial No. 501,658

6 Claims.

This invention relates to methods of and means for checking the receipt of consecutively numbered messages and for automatically producing an indication by sounding an alarm or otherwise automatically producing an efiect to indicate the failure of the automatic apparatus to verify the receipt of any one of a number of consecutively numbered messages.

It is old in the telegraph art to transmit at the head end of each of a number of messages going over a particular communication channel a number designating the serial number of the message on that channel for the particular day or other period of time. The usual practice is to begin the days transmission with message Messages may be and often are numbered consecutively by the sending operator or in the case of tape transmission where the tapes are collected from a variety of incoming reperforators or local perforators by splicing codes representing the required number at the head end of each message in the form of extra codes representing the number. Alternatively the numbers of the messages may be transmitted by a keyboard sender included in the line at the sending end or the entire messages including the numbers may be transmitted from a keyboard operated transmitter. Furthermore, automatic numbering systems have been described in telegraph literature by which messages transmitted over a channel of transmission are automatically consecutively numbered. I

In all such systems it may be desirable or advantageous to provide .at a receiving system automatic means for verifying the receipt of such messages in the desired numerical order and sounding an alarm, giving an indication, or producing some other action in case a messa e of the series is received without the number which should accompany it as the next consecutive message of the series.

An object of the invention is to provide methods of and equipment for checking the receipt of messages numbered, lettered or otherwise designated by consecutive identifications. The methods and apparatus of the invention as described herein in an exemplary form are equally applicable for the intended purpose regardless of the method by which the messages are originally numbered, whether automatic or otherwise.

In the exemplary embodiment as described, numbered messages arriving over an incoming line operate the selector magnet of an instrument commonly known as a typing reperforator. Associated with the typing reperforator are a letters contact, that is, a contact closed by the platen so long as it remains in the letters or lower case code position, a universal contact, and two other contacts closed by the platen of the receiving instrument in figures and letters position. A relay system and other instrumentalities interassociate these contacts with a system of pull bar contacts which are closed under control of the message numbers in consecutive order and a series of contacts closed under the control of end-of-message signals and stepping switches. These numerical contacts are set initially at 00 or 01, or any other number which is to be the number of the first message and are stepped forward after completion of the registration of the number of each message to the next contact andso on to check the identification of each message of a series. In case the number of any message is not correctly received as would be the case if the whole message were lost or if the number were erroneously transmitted, an alarm is sounded.

Complete automatic operation of a system of this type of end-of-message signal is essential 1n order that the equipment may recognize the termination of one message in order to step the numerical number checking equipment forward to check the number of the next message. For ordinary messages in plain language and for purposes other than automatically checking the numbers of messages an end-of-message indication, such as upper case J or other end-of-message signal consisting of one, two or three specially selected code combinations, have been used in other systems and might be used herein. However,.there is a demand in certain fields for transmission of telegraph messages in cipher. In such systems practically all code combinations and simple successions of code combinations are likely to occur with reasonable frequency in the ciphered text for which reason a simple end-ofmessage signal would not be practicable because it might occur from time to time in the ciphered text and thus give false indications.

A feature of the present invention consists of an end-of-message signal which will occur in cipher transmission with such extraordinary infrequency that its use is practicable. This feature of the invention is of broad applicability whenever any end-of-message signal is required for cipher transmission. Specifically, in the exemplary embodiment the end-of-message signal comprises a letters signal eight times repeated with no other code combination needed. With random cipher transmission the probability is essentials of the circuit arrangement useful for circuit transmission.

Instrumentalities utilized in this circuit arrangement are conventional pieces of equipment generally known to telegraph h this reason need no detailed desc iption.

Aline or circuit I indicates generally a line circuit or channel over which messages in startstop permutation code are incoming. specifical 1y, it may be assumed that these messages are in plain text and that at the beginning of each message is a number representing the ordinal or serial number of that message in the sequence of messages and at the end of each message is a series of eight or more consecutive letters code combinations. Let us assume that at the beginning of operation; stepping switch 2 is positioned on its No. 1 contact and a stepping switch 3 is on its zero contact. The typing reperforator which is actuated by the selector magnet TRS has a series of contacts UN to SN,in'clusive-, which are actuated by receipt of the code combination corresponding to the respective numbers. The switches 2 and 3 may be provided or associated with manually operable keys 5K and 6K for setting them in any desired position "at the beginning of operation or at any other time.

At the beginning of operation the units switcharm IIU maybe set on its contact No. 1 by operation of key SK and the tens switch IZU may be similarly set on contact fl, 'thu's setting up the number IlI corresponding to the number of the first message. Prior'to message transmission over line or channel I; the operator or attendant at the distant station will transmit or cause to be transmitted eight Letters code combinations. The selector magnet TRS will respond to the incoming code combinations and actuate a startstop selector mechanism (not shown but well understood to those skilled in the art) to close the contact 4', whichis pull-bar operated on the Letters combination, eight times in succession thus energizing and releasing the stepping magnet l eight times, stepping the arm of switch SW9 up to its eighth contact. When this occurs battery will be supplied to operate relay i9. Relay is will lockup over the back contact of relay I3, supply battery to energize the stepping magnet I! and supply battery to a conductor IOa. Stepping magnet II is of the type which steps its associated switch-arm upon release. The energization of the magnet produces no effect except to prepare for stepping the switch upon release. Likewise, battery applied to conductor Illa produces no eiiect at the instant of its application.

Let us now suppose that the first message is preceded by the message designating codes Figs, the code for 0, and the code for numeral 1. When the Figs. code actuates the selector mechanism it will function to close the universal contact 6 which energizes the release magnet 8 which restores the arm of switch SW9 back to its zero contact. The Figs. signal also closes the contact I4 which supplies battery to actuate the slow-release relay I5. The actuation of slowrelease relay I5 closes its contacts and presents battery to the winding of relay I5 which does not operate at this time because none of the numerical contacts (IN, IN, 2N, etc. is closed. With the Figs. contact remaining closed the code combination for zero is now received and interpreted by the selecting mechanism to close the tens contact UN to which the arm I2U is now connected. This closes the circuit from conductor Inc to energize, relay I5 through the lefthand baekeontactof relay I'I. Relay I6 prepares a locking contact for itself, through the winding of relay H, but relay I! does not operate at this time because the ground connection through contact 0N short-circuits its winding. When contact I 0N reopens as its pull bar is restored to normal, relay H willoperate.

Conditions are now established for receipt of the units code combination or numeral 1. Inasmuch a relay I5 remains energized at this time, receipt of numeral 1 causing the closing of numeral contact IN will cause the operation of relay I3 as follows: From ground over contact IN of the typing reperforator, contact 'iU upon which the arm IIU of switch 2 is assumed to be standing, winding of relay I3, front contact of relay H, to conductor IBa. Immediately after the opening of contact ON the contact IN is closed by the selection of the numeral 1 and activation of the corresponding pull' bar. The operation of relay I3 as'just described, opens the path through operating windingof relay 18, said path extending through a front contact of slow-release relay [5 through'a platen Contact I9 which is closed only when the letters code has moved the platen to the letters or lowercase position. The next code combination following the number designation is always assumed to be a letters signal which opens the circuit through the winding of the slow-release relay I5'and'eloses contact I9. However, inasmuch as the relay I3 had operated to open 'tli e'path through the winding of relay id at the {front contact of relay I3 and also because the relay I'Uhas been released by the operation of Now let us eonsid'er what happens when a fals'e'n'u'mber signal is received immediately after the "eight letters code-combination had preceded the transmissionof the first message. Relay It will then be opierated and the next figures signal will operate relay I5. Then if the tens digit of the message number were not correct, the relay I6 would notenergize with theobvious result thattherelay 13 would not have been energized upon'reception of the units digit whether the'units 'digit was or was not correctly received. And, furthermo jefifthe'units'digit received was not correct, that is, if it did notc'orre'spond to the'settingfof thearm fIj'IU, relay I3 could not be energized and upon the return of platen to the letters positionupon the succeeding letters signal, relay I8 would be eriergized'bec'ause ina's'muc'h as the relay 1 3did'iiot operate the "relay Ill continued to be locked an'd'to supply battery to the conductor "Illa. Upon operation of the relay I8, it closes a'tfi'ts 'fr'o'fitcontact 'a path through an alarm device "such 'as a light or bell which continues to'b'e closed until an attendant recognizes that the system had registered a failure to check the number of the message just re ceivecl as being correct and operates a key 20 to open the-alarm circuit and release relay I 8.

Thus, a systemishprovided in which consecut ively numbered messages may be automatically checked oii, one by one, with the production of p a suitable indication incase thenumber of any message does not check. In ease the circuit l' incoming Tfrom'a remote stationv is set upon a half-duplex basis, the alarm circuit may include a contact which controls the sending of a break signal back over the channel I thus interrupting transmission at the remote station in addition to registering the alarm at the station illustrated. Other features, as may be desired, may be added in the alarm circuit by methods well known in the art, as for example, aloud ringing bell common to the office and arranged to be operated when relay I8 of any circuit in the ofiice is operated.

vIt will be understood that for each release of relay I0 stepping switch II will advance the arm IIU one step. Another arm IIUI moves over a series of contacts of which onlythe No. 9 contact is connected to a stepping magnet 2| which thus becomes energized when the arm HUI reaches the No. 9 contact. Whenever the arm HUI steps off the No. 9 contact, the magnet 2| will be released and step the arm IZU one step forward.-

As illustrated, the arrangement will repeatthe numbers for every one hundred messages, the one hundredth message being numbered 00 because at this time both arms U and iZU will stand upon their zero contacts. In so far as described the selector magnet TRS has been assumed to be the magnet of a typing reperforator which produces a perforated tape which isa record of all the incoming code combinations. From this tape messages may be read inasmuch as a well-known type of typing reperforator in use prints the message legibly upon the tape or the same tape may be used in an automatic or machine transmitter to control the retransmis- I sion of the message over another circuit or channel. The tape from the typing reperforator may extend directly intoan associated retransmitter.

(not shown) with the intervention of a tape stop arm. In such arrangements there are sometimes employed a device for causing the reperforator to step out the additionaltape at the end of the message. Such stepping out of additional tape may be controlled by a manual key or push-button. In the case whereinv the stepping out of additional tape causes the tape to be impressed with letters signals by operating the selector magnet TRS locally in accordance with letters It will be noted that the switch SW9 responds to an end-of-message signal which consists of eight consecutive letters code combinations with no other code combination intervening. For ordinary transmission of plain text, the switch SW9 could be replaced by a contact which responds to a more conventional end-of-message signal such as Figs. J (upper case J). However, in systems wherein the message transmitted consists of ciphered codes and especially in the case of random cipher codes, upper case J or any other conventional simple -end-ofmessage signal is likely to occur at relatively frequent intervals with the result that false end-ofmes'sage signals would be registered. However, by using eight consecutiveletters'signals as an end-ofof the messages are to be transmitted together message signal, false end-of-message signals would seldom occur with random ciphering. The probability of any code combination being a letters signal a ciphered message is one in thirtytwo and the probability that eight consecutive letters signal would occur in such transmission would be one in 32 characters or codes. Thus a false end-of -message signal would occur, on the"average, only once in considerably over a thousand billion characters. This probability may be slightly, but unimportantly, increased by the fact that the first code combination preceding the ciphered message would be a letters code: combination, possibly at the most two letters. code combinations. In such case, ifthe succeeding ciphered transmission consisted of seven or perhaps six consecutive letters code combina-- tions, a false end-of-message indication might. be given. This probability is very small and, of. course, applies only at the beginning of a mes-- sage because upon the occurrence of any other character the efiect of the specially introduced. letters signal or signals at the beginning is an-- nulled.

In utilizing the present system for cipher trans-- mission, it is contemplated that a special routine will be observed. In accordance with this routine the operator at the sending station will transmit eight or more letters codes at the beginning of the days run followed by the upper case or figures code, followed in turn by the.

number of the message, followed in turn by a.

single letters code. Ordinarily, it is convenient in. the transmission of random ciphered code and its deciphering by the deciphering instrumentalities at the receiving end that the decipher-- ing instrumentalities be started in a definite case condition, i. e., the letters or lower case condition. which is most convenient for this purpose.

In the case of transmission from an automatic: tape controlled transmitter, if the sending operator or attendant happens to be provided with a. perforated tape representing a ciphered message: to be sent, the operator may splice onto the head. end of the tape one or more figures codes followed by the number of the message, followed by a single letters code and may splice onto the! trailing end of the tape the necessary eight letters codes to constitute the end-of-message signal. Alternately, however, the operator may transmit these various elements from a keyboard from time to time.

At the receiving station illustrated in the draw-- ing, the receiving machine will produce an enciphered tape having control codes at the front; and at the trailing end thereof. This messagemay be deciphered in the usual manner by send-- ing it into a local circuit in combination with: a deciphering tape which circuit is connected'to. a printer. In this case, in order to start the: deciphering tape, the message number and let-- ters signal at the head end of the tape will ordinarily be disregarded, the deciphering starting at the first code combination of the ciphered message. However, it will be obvious that if all the incoming message are to be retransmitted in the same order over another circuit at the receiving end, the message checking instrumen-- talities in the tape may be used for this purposewithout alteration and, furthermore, if only part with other messages, all the messages may be provided with-suitable consecutive numbers and retransmitted to another station at which a simi- 

